Method for preparing molecular sieve SSZ-87

ABSTRACT

This disclosure is directed to a method for preparing a new crystalline molecular sieve designated SSZ-87, which is synthesized using an N,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium dication as a structure directing agent.

TECHNICAL FIELD

This disclosure relates to a new crystalline molecular sieve designatedSSZ-87, a method for preparing SSZ-87 using anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication as a structure directing agent (“SDA”) and uses for SSZ-87.

BACKGROUND

Because of their unique sieving characteristics, as well as theircatalytic properties, crystalline molecular sieves and zeolites areespecially useful in applications such as hydrocarbon conversion, gasdrying and separation. Although many different crystalline molecularsieves have been disclosed, there is a continuing need for new molecularsieves with desirable properties for gas separation and drying,hydrocarbon and chemical conversions, and other applications. Newmolecular sieves can contain novel internal pore architectures,providing enhanced selectivities in these processes.

SUMMARY

The present disclosure is directed to a new family of crystallinemolecular sieves with unique properties, referred to herein as“molecular sieve SSZ-87” or simply “SSZ-87.”

In one aspect, there is provided a molecular sieve having a mole ratioof 10 or greater of (1) at least one oxide of at least one tetravalentelement to (2) optionally, one or more oxides selected from the groupconsisting of oxides of trivalent elements, pentavalent elements, andmixtures thereof, and having, in its calcined form, the powder X-raydiffraction (XRD) lines of Table 4. It should be noted that the phrase“mole ratio of 10 or greater” includes the case where there is no oxide(2), i.e., the mole ratio of oxide (1) to oxide (2) is infinity. In thatcase, the molecular sieve is comprised of essentially all of the oxideof one or more tetravalent elements.

In another aspect, there is provided a method for preparing a molecularsieve by contacting under crystallization conditions (1) at least onesource of silicon; (2) at least one source of boron; (3) fluoride ions;and (4) anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication.

In yet another aspect, there is provided a process for preparing amolecular sieve having, in its calcined form, the powder XRD lines ofTable 4, by: (a) preparing a reaction mixture containing: (1) at leastone source of silicon; (2) at least one source of boron; (3) fluorideions; (4) anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication; and (5) water; and (b) maintaining the reaction mixture underconditions sufficient to form crystals of the molecular sieve.

Where the molecular sieve formed is an intermediate material, theprocess disclosed herein includes a further post-crystallizationprocessing step in order to achieve the target molecular sieve (e.g., bypost-crystallization heteroatom lattice substitution or acid leaching).

There is also provided a novel molecular sieve designated SSZ-87 havinga composition, as-synthesized and in its anhydrous state, in terms ofmole ratios, as follows:

Broad Secondary SiO₂/B₂O₃  10 to 200  10 to 100 Q/SiO₂ 0.015 to 0.060.025 to 0.06wherein Q is anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the powder XRD pattern of the as-synthesized borosilicateSSZ-87 product of Example 1.

FIG. 2 shows the powder XRD pattern of the calcined borosilicate SSZ-87product of Example 4.

FIG. 3 shows the scanning electron microscopy (SEM) image of thecalcined borosilicate SSZ-87 product of Example 4.

DETAILED DESCRIPTION

Introduction

The following terms will be used throughout the specification and willhave the following meanings unless otherwise indicated.

The term “active source” means a reagent or precursor material capableof supplying an element in a form that can react and be incorporatedinto the molecular sieve structure. The terms “source” and “activesource” are used interchangeably herein.

The term “Periodic Table” refers to the version of the IUPAC PeriodicTable of the Elements dated Jun. 22, 2007, and the numbering scheme forthe Periodic Table Groups is as described in Chem. Eng. News 63(5),26-27 (1985).

The term “molecular sieve” includes (a) intermediate and (b) final ortarget molecular sieves and molecular sieves produced by (1) directsynthesis or (2) post-crystallization treatment (secondary synthesis).Secondary synthesis techniques allow for the synthesis of a targetmaterial from an intermediate material by heteroatom latticesubstitution or other techniques. For example, an aluminosilicate can besynthesized from an intermediate borosilicate by post-crystallizationheteroatom lattice substitution of the boron for aluminum. Suchtechniques are known, for example as described in U.S. Pat. No.6,790,433.

This disclosure is directed to a molecular sieve designated herein as“molecular sieve SSZ-87” or simply “SSZ-87.”

In preparing SSZ-87, anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication is used as a structure directing agent (“SDA”), also known as acrystallization template. The SDA useful for making SSZ-87 isrepresented by the following structure (1):

The SDA dication is associated with anions which can be any anion thatis not detrimental to the formation of SSZ-87. Representative anionsinclude those from Group 17 of the Periodic Table (e.g., fluoride,chloride, bromide and iodide), hydroxide, acetate, sulfate,tetrafluoroborate, carboxylate, and the like.

TheN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication can be synthesized from, for example,bicyclo[2.2.2]oct-7-ene-2,3:5,6-tetracarboxylic dianhydride, which is acommercially available material. For instance, theN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication can be prepared from the dianhydride which is initially reactedwith isopropylamine to produce the bicyclo N,N′-disopropyl diimide whichis then reduced with LiAlH₄ to produce the diamine. The diamine can thenbe alkylated with an ethyl halide (e.g., iodoethane) to produce theN,N′-diisopropyl-N,N′-diethyl quaternary dication. Such methods areknown, for example as described in U.S. Pat. No. 6,656,268.

Reaction Mixture

In general, SSZ-87 is prepared by: (a) preparing a reaction mixturecontaining (1) at least one source of silicon; (2) at least one sourceof boron; (3) fluoride ions; (4) anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication; and (5) water; and (b) maintaining the reaction mixture underconditions sufficient to form crystals of the molecular sieve.

Where the molecular sieve formed is an intermediate molecular sieve, theprocess includes a further step of synthesizing a target molecular sieveby post-synthesis techniques, such as heteroatom lattice substitutiontechniques and acid leaching.

The composition of the reaction mixture from which the molecular sieveis formed, in terms of molar ratios, is identified in Table 1 below:

TABLE 1 Reactants Broad Secondary SiO₂/B₂O₃   5 to 100 10 to 60 Q/SiO₂0.05 to 0.5 0.1 to 0.4 F/SiO₂ 0.05 to 0.5 0.1 to 0.4 H₂O/SiO₂  10 to 10015 to 25wherein compositional variable Q is as described herein above.

Sources useful herein for silicon include fumed silica, precipitatedsilicates, silica hydrogel, silicic acid, colloidal silica, tetra-alkylorthosilicates (e.g., tetraethyl orthosilicate), and silica hydroxides.

Sources of boron which can be useful include borosilicate glasses,alkali borates, boric acid, borate esters, and certain molecular sieves.Non-limiting examples of a source of boron oxide include potassiumtetraborate decahydrate and boron beta molecular sieve (B-beta molecularsieve).

Sources useful herein for fluoride ions (F) include hydrogen fluorideand ammonium fluoride.

For each embodiment described herein, the molecular sieve reactionmixture can be supplied by more than one source. Also, two or morereaction components can be provided by one source. For example,borosilicate molecular sieves may be synthesized by the method describedherein using boron-containing beta zeolite as taught in U.S. Pat. No.5,972,204.

The reaction mixture can be prepared either batch wise or continuously.Crystal size, morphology and crystallization time of the molecular sievedescribed herein can vary with the nature of the reaction mixture andthe crystallization conditions.

Crystallization and Post-Synthesis Treatment

In practice, the molecular sieve is prepared by: (a) preparing areaction mixture as described herein above; and (b) maintaining thereaction mixture under crystallization conditions sufficient to formcrystals of the molecular sieve.

The reaction mixture is maintained at an elevated temperature until thecrystals of the molecular sieve are formed. The hydrothermalcrystallization is usually conducted under pressure, and usually in anautoclave so that the reaction mixture is subject to autogenouspressure, at a temperature between 125° C. and 200° C.

The reaction mixture can be subjected to mild stirring or agitationduring the crystallization step. It will be understood by a personskilled in the art that the molecular sieves described herein cancontain impurities, such as amorphous materials, unit cells havingframework topologies which do not coincide with the molecular sieve,and/or other impurities (e.g., organic hydrocarbons).

During the hydrothermal crystallization step, the molecular sievecrystals can be allowed to nucleate spontaneously from the reactionmixture. The use of crystals of the molecular sieve as seed material canbe advantageous in decreasing the time necessary for completecrystallization to occur. In addition, seeding can lead to an increasedpurity of the product obtained by promoting the nucleation and/orformation of the molecular sieve over any undesired phases. When used asseeds, seed crystals are added in an amount between 1% and 10% of theweight of the source for silicon used in the reaction mixture.

Once the molecular sieve crystals have formed, the solid product isseparated from the reaction mixture by standard mechanical separationtechniques such as filtration. The crystals are water-washed and thendried to obtain the as-synthesized molecular sieve crystals. The dryingstep can be performed at atmospheric pressure or under vacuum.

The molecular sieve can be used as-synthesized, but typically will bethermally treated (calcined). The term “as-synthesized” refers to themolecular sieve in its form after crystallization, prior to removal ofthe SDA cation. The SDA can be removed by thermal treatment (e.g.,calcination), preferably in an oxidative atmosphere (e.g., air, gas withan oxygen partial pressure of greater than 0 kPa) at a temperaturereadily determinable by one skilled in the art sufficient to remove theSDA from the molecular sieve. The SDA can also be removed by photolysistechniques (e.g., exposing the SDA-containing molecular sieve product tolight or electromagnetic radiation that has a wavelength shorter thanvisible light under conditions sufficient to selectively remove theorganic compound from the molecular sieve) as described in U.S. Pat. No.6,960,327.

The molecular sieve can subsequently be calcined in steam, air or inertgas at temperatures ranging from 200° C. to 800° C. for periods of timeranging from 1 to 48 hours, or more.

Where the molecular sieve formed is an intermediate molecular sieve, thetarget molecular sieve can be achieved using post-synthesis techniquessuch as heteroatom lattice substitution techniques. The target molecularsieve (e.g., silicate SSZ-87) can also be achieved by removingheteroatoms from the lattice by known techniques such as acid leaching.

The molecular sieve made from the process described herein can be formedinto a wide variety of physical shapes. Generally speaking, themolecular sieve can be in the form of a powder, a granule, or a moldedproduct, such as extrudate having a particle size sufficient to passthrough a 2-mesh (Tyler) screen and be retained on a 400-mesh (Tyler)screen. In cases where the catalyst is molded, such as by extrusion withan organic binder, the molecular sieve can be extruded before drying,or, dried or partially dried and then extruded.

The molecular sieve can be composited with other materials resistant tothe temperatures and other conditions employed in organic conversionprocesses. Such matrix materials include active and inactive materialsand synthetic or naturally occurring zeolites as well as inorganicmaterials such as clays, silica and metal oxides. Examples of suchmaterials and the manner in which they can be used are disclosed in U.S.Pat. Nos. 4,910,006 and 5,316,753.

SSZ-87 is useful in catalysts for a variety of hydrocarbon conversionreactions such as hydrocracking, dewaxing, olefin isomerization,alkylation of aromatic compounds and the like. SSZ-87 is also useful asan adsorbent for separations.

Characterization of the Molecular Sieve

Molecular sieves made by the process described herein have acomposition, as-synthesized and in the anhydrous state, as described inTable 2 (in terms of mole ratios), wherein compositional variable Q isas described herein above:

TABLE 2 Broad Secondary SiO₂/B₂O₃  10 to 200  10 to 150 Q/SiO₂ 0.015 to0.06 0.025 to 0.06

SSZ-87 can be an essentially all-silica material. As used herein,“essentially all-silica” or “essentially all silicon oxide” means thatthe molecular sieve's crystal structure is comprised of only siliconoxide, or is comprised of silicon oxide and only a trace amount of otheroxides, such as aluminum oxide, which can be introduced as impurities inthe source of silicon oxide. Thus, in a typical case where oxides ofsilicon and boron are used, SSZ-87 can be made essentially boron-free,i.e., having a silicon oxide to boron oxide mole ratio of ∞. SSZ-87 ismade as a borosilicate and then the boron can be removed, if desired, bytreating the borosilicate SSZ-87 with acetic acid at elevatedtemperature (as described by C. W. Jones et al. in Chem. Mater. 2001,13, 1041-1050) to produce an essentially all-silica version of SSZ-87.

If desired, SSZ-87 can be made as a borosilicate and then the boron canbe removed as described above and replaced with metal atoms bytechniques known in the art. Aluminum, gallium, indium, and mixturesthereof can be added in this manner.

Molecular sieves synthesized by the process described herein arecharacterized by their X-ray diffraction pattern. The X-ray diffractionpattern lines of Table 3 are representative of as-synthesized SSZ-87.Minor variations in the diffraction pattern can result from variationsin the mole ratios of the framework species of the particular sample dueto changes in lattice constants. In addition, sufficiently smallcrystals will affect the shape and intensity of peaks, leading tosignificant peak broadening. Minor variations in the diffraction patterncan also result from variations in the organic compound used in thepreparation and from variations in the Si/B mole ratio from sample tosample. Calcination can also cause minor shifts in the X-ray diffractionpattern. Notwithstanding these minor perturbations, the basic crystallattice structure remains unchanged.

TABLE 3 Characteristic Peaks for As-Synthesized SSZ-87 2-Theta^((a))d-Spacing, nm Relative Intensity^((b)) 7.02 1.257 M 8.74 1.010 S 13.230.669 W 15.71 0.564 W 16.06 0.552 W 16.82 0.527 W 17.49 0.507 W 19.430.457 VS 21.62 0.411 VS 22.26 0.399 M 24.55 0.362 M 25.20 0.353 W 26.120.341 M 26.83 0.332 W 28.22 0.316 W 28.54 0.312 W 29.94 0.298 W^((a))±0.20 degrees ^((b))The powder XRD patterns provided are based ona relative intensity scale in which the strongest line in the X-raypattern is assigned a value of 100: W = weak (>0 to ≦20); M = medium(>20 to ≦40); S = strong (>40 to ≦60); VS = very strong (>60 to ≦100).

The X-ray diffraction pattern lines of Table 4 are representative ofcalcined SSZ-87.

TABLE 4 Characteristic Peaks for Calcined SSZ-87 2-Theta^((a))d-Spacing, nm Relative Intensity^((b)) 7.09 1.245 VS 8.78 1.006 S 9.950.889 W 13.36 0.662 W 16.04 0.553 W 16.88 0.525 W 17.51 0.506 W 19.480.455 VS 21.65 0.410 VS 22.24 0.399 M 24.52 0.363 M 25.17 0.354 W 26.170.340 M 26.87 0.331 M 28.28 0.315 W 28.58 0.312 W 29.94 0.298 M^((a))±0.20 degrees ^((b)) The powder XRD patterns provided are based ona relative intensity scale in which the strongest line in the X-raypattern is assigned a value of 100: W = weak (>0 to ≦20); M = medium(>20 to ≦40); S = strong (>40 to ≦60); VS = very strong (>60 to ≦100).

The powder X-ray diffraction patterns presented herein were collected bystandard techniques. The radiation was CuK_(α) radiation. The peakheights and the positions, as a function of 2θ where θ is the Braggangle, were read from the relative intensities of the peaks, and d, theinterplanar spacing in Angstroms corresponding to the recorded lines,can be calculated.

EXAMPLES

The following illustrative examples are intended to be non-limiting.

Example 1 Synthesis of Borosilicate SSZ-87 (B-SSZ-87)

4.5 mmol ofN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdihydroxide and 14 mmol of tetraethyl orthosilicate were added to aTeflon container. Next, 1 mmol of boric acid and 4.5 mmol of ammoniumfluoride were added to the container. The mixture was allowed to standin a closed configuration. After two days, the top was opened andethanol was allowed to evaporate. The H₂O/SiO₂ mole ratio was thenadjusted to 20. The Teflon liner was then capped and sealed within asteel Parr autoclave. The autoclave was placed on a spit within aconvection oven at 160° C. The autoclave was tumbled at 43 rpm over thecourse of 38 days in the heated oven. The autoclave was then removed andallowed to cool to room temperature. The solids were then recovered byfiltration and washed thoroughly with deionized water. The solids wereallowed to dry at room temperature.

The resulting product was analyzed by powder XRD. FIG. 1 shows thepowder XRD pattern of the as-synthesized product of this Example. Table5 below shows the powder XRD diffraction lines for the resultingproduct.

Elemental analysis indicated the product contained 37.9% Si and 0.757%B. CHN combustion analysis indicated the as-made product contained11.34% C, 2.13% H and 1.24% N.

TABLE 5 2-Theta^((a)) d-Spacing, nm Relative Intensity (%) 7.02 1.25734.9 8.74 1.010 45.0 13.23 0.669 18.7 15.71 0.564 11.7 16.06 0.552 6.116.82 0.527 16.2 17.49 0.507 9.3 19.43 0.457 100.0 21.62 0.411 81.522.26 0.399 21.2 24.55 0.362 20.2 25.20 0.353 6.4 26.12 0.341 26.3 26.830.332 18.3 28.22 0.316 2.3 28.54 0.312 6.9 29.94 0.298 15.8 ^((a))±0.20

Example 2 Synthesis of SSZ-87 with Seeding

Example 1 was repeated except that seeds of SSZ-87 from a previoussynthesis were added to the reaction mixture at about 3 wt. %. Thecrystalline product was formed in about two weeks.

Example 3 Synthesis Using a Concentrated Preparation

Example 1 was repeated except that the H₂O/SiO₂ mole ratio was reducedto about 5. No SSZ-87 seed material was added to this preparation. Afterabout 6 weeks of reaction, the product collected was seen to be aversion of MTW.

Example 4 Calcination of SSZ-87

The product of Example 1 was calcined in a muffle furnace under a flowof 2% oxygen/98% nitrogen heated at 595° C. at a rate of 1° C./min andheld at 595° C. for five hours, cooled and then analyzed by powder XRD.The resulting XRD pattern is shown in FIG. 2. The powder XRD patternindicates that the material remained stable after calcination to removethe organic SDA. Table 6 below shows the powder XRD diffraction linesfor the calcined product.

TABLE 6 2-Theta^((a)) d-Spacing, nm Relative Intensity (%) 7.09 1.24584.7 8.78 1.006 58.3 9.95 0.889 6.3 13.36 0.662 16.9 16.04 0.553 11.016.88 0.525 10.9 17.51 0.506 9.0 19.48 0.455 100.0 21.65 0.410 85.822.24 0.399 30.3 24.52 0.363 22.9 25.17 0.354 11.2 26.17 0.340 32.226.87 0.331 22.1 28.28 0.315 5.2 28.58 0.312 8.2 29.94 0.298 22.3^((a))±0.20

Example 5 Micropore Volume Determination

Calcined SSZ-87 of Example 4 was subjected to a surface area andmicropore volume analysis using N₂ as adsorbate and via the BET method.A t-plot analysis of nitrogen physisorption data of the calcined productof Example 4 indicated a micropore volume of 0.17 cm³/g and an externalBET surface area of 446 m²/g. It can be seen that the calcined SSZ-87has considerable porosity and external surface area. This is consistentwith a very small crystal morphology which can be seen in the SEM of theproduct (FIG. 3).

Example 6 Al-Exchange of B-SSZ-87

The calcined borosilicate product of Example 4 was then converted to thealuminosilicate form following a procedure similar to that reported inU.S. Pat. No. 6,790,433. The resulting aluminum-containing SSZ-87product was then washed with dilute HCl and then water, filtered anddried at room temperature in a vacuum filter. The powder XRD pattern wasessentially the same as that of FIG. 2 except the introduction ofaluminum for boron can be seen to change the lattice constants for thealuminosilicate product. Elemental analysis indicated the productcontained 38.6% Si and 1.12% Al.

Example 7 Constraint Index Determination

The aluminosilicate product of Example 6 was pelletized at 4-5 kpsi andcrushed and meshed to 20-40. 0.50 g was packed into a ⅜ inch stainlesssteel tube with alundum on both sides of the molecular sieve bed. ALindburg furnace was used to heat the reactor tube. Helium wasintroduced into the reactor tube at 10 mL/min and at atmosphericpressure. The reactor was heated to about 371° C. and a 50/50 (w/w) feedof n-hexane and 3-methylpentane was introduced into the reactor at arate of 8 μL/min. Feed delivery was made via a Brownlee pump. Directsampling into a gas chromatograph (GC) began after 10 minutes of feedintroduction. The Constraint Index value (not including 2-methylpentane)was calculated from the GC data using methods known in the art and wasfound to be between 1.11 and 0.89 for times on stream from 10 to 100minutes. At 371° C. and 10 minutes on stream, feed conversion wasgreater than 50%, with a selectivity value near one. This indicates thatthe pore system of this material is larger than intermediate, but it isstill hindered compared to open large pore molecular sieves.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained. It is noted that, as used inthis specification and the appended claims, the singular forms “a,”“an,” and “the,” include plural references unless expressly andunequivocally limited to one referent. As used herein, the term“include” and its grammatical variants are intended to be non-limiting,such that recitation of items in a list is not to the exclusion of otherlike items that can be substituted or added to the listed items. As usedherein, the term “comprising” means including elements or steps that areidentified following that term, but any such elements or steps are notexhaustive, and an embodiment can include other elements or steps.

Unless otherwise specified, the recitation of a genus of elements,materials or other components, from which an individual component ormixture of components can be selected, is intended to include allpossible sub-generic combinations of the listed components and mixturesthereof.

The patentable scope is defined by the claims, and can include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal languages of the claims. To an extent notinconsistent herewith, all citations referred to herein are herebyincorporated by reference.

The invention claimed is:
 1. A method of preparing a molecular sievecomprising contacting under crystallization conditions (1) at least onesource of silicon; (2) at least one source of boron; (3) fluoride ions;and (4) anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication; wherein the molecular sieve has, in its calcined form, anX-ray diffraction pattern substantially as shown in the following table:2-Theta d-Spacing, nm Relative Intensity  7.09 ± 0.20 1.245 VS  8.78 ±0.20 1.006 S  9.95 ± 0.20 0.889 W 13.36 ± 0.20 0.662 W 16.04 ± 0.200.553 W 16.88 ± 0.20 0.525 W 17.51 ± 0.20 0.506 W 19.48 ± 0.20 0.455 VS21.65 ± 0.20 0.410 VS 22.24 ± 0.20 0.399 M 24.52 ± 0.20 0.363 M 25.17 ±0.20 0.354 W 26.17 ± 0.20 0.340 M 26.87 ± 0.20 0.331 M 28.28 ± 0.200.315 W 28.58 ± 0.20 0.312 W 29.94 ± 0.20 0.298 M.


2. The method of claim 1, wherein the molecular sieve is prepared from areaction mixture comprising, in terms of mole ratios, the following:SiO₂/B₂O₃   5 to 100 Q/SO₂ 0.05 to 0.5 F/SiO₂ 0.05 to 0.5 H₂O/SiO₂  10to 100

wherein Q is anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication.
 3. The method of claim 1, wherein the molecular sieve isprepared from a reaction mixture comprising, in terms of mole ratios,the following: SiO₂/B₂O₃ 10 to 60 Q/SiO₂ 0.1 to 0.4 F/SiO₂ 0.1 to 0.4H₂O/SiO₂ 15 to 25

wherein Q is anN,N′-diisopropyl-N,N′-diethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidiniumdication.